public class test1 {
    public static void main(String[] args) {
        String s1, s2, t1="ABCDabcd";
        s1=t1.toUpperCase () ;
        s2=t1.toLowerCase () ;
        System.out.println (s1);
        System.out.println (s2);
        String s3=s1. concat (s2);
        System. out.println (s3);
    }
}